1. Field of the Invention
The present invention relates to liquid droplet flight devices and liquid droplet flight methods that are used in image forming apparatuses such as copiers, printer apparatuses, and facsimile machines to induce flight of liquid droplets such as ink liquid droplets, and particularly relates liquid droplet flight devices and liquid droplet flight methods capable of stably forming high image quality images by causing stable flight of liquid droplets using an electrostatic attraction method.
2. Description of the Related Art
Methods such as piezo conversion and electrostatic attraction are used in inkjet method image forming apparatuses in which ink is caused to fly so as to form an image. An electrostatic method inkjet image forming apparatus shown in Japanese Patent Application Laid-open No. H11-198381 (referred to as Prior Art 1) is provided with a plurality of electrodes arranged on an ink discharge outlet side and an opposing electrode arranged in a position in opposition to leading end portions of these electrodes, and a high voltage of 1800 V for example is applied to electrodes arranged in positions near electrodes that are to form an ink discharge point at which ink is to be discharged in order to eliminate flight of ink from unintended electrodes, thereby lowering the electric potential of ink discharge points below that of electrodes arranged in nearby positions and reducing the ink at the leading ends of nearby electrodes at which ink has accumulated at the ink discharge points such that a discharge meniscus forms at the ink discharge points and ink liquid droplets are caused to fly from electrodes at the ink discharge points.
Furthermore, Japanese Patent Application Laid-open No. 2004-165587 (referred to as Prior Art 2) discloses a hyperfine liquid jet apparatus in which ink liquid droplets are discharged using an electrostatic attraction method and an electrowetting effect. The hyperfine liquid jet apparatus shown in Prior Art 2 is configured such that a flight electrode is provided inside hyperfine diameter nozzles that supply a liquid, and an electrode that covers a leading end outer side is provided outside the hyperfine diameter nozzles, and a substrate constituted by an opposing electrode is arranged at a distance of 0.05 mm or less from the leading ends of the hyperfine diameter nozzles. Then, by controlling a voltage to be applied to the electrodes provided at the leading end outer side of the hyperfine diameter nozzles and achieving an electrowetting effect, the liquid inside the hyperfine diameter nozzles moves to the opposing electrode side, and liquid droplets are caused to fly by locally increasing the strength of an electric field.
The image forming apparatus shown in Prior Art 1 requires a pulse drive device to apply a high voltage pulse voltage in order to discharge ink, which is disadvantageous in that it involves high costs and offers poor frequency responsiveness.
Furthermore, in order cause movement of the liquid using an electrowetting effect inside the hyperfine diameter nozzles, the hyperfine liquid jet apparatus shown in Prior Art 2 requires a comparatively high voltage of approximately 300 V so to be capable of creating a capillary phenomenon and to achieve resistance to enable the electrowetting effect. Furthermore, this is difficult to apply to high viscosity inks.